Field of Invention
The present invention relates to a reflective display device.
Description of Related Art
In a market full of a wide variety of consumer electronic products, electrophoretic display devices have been extensively utilized as display screens in electronic products. A display medium layer of an electrophoretic display device is formed of the main elements of an electrophoresis buffer and white and black charged particles doped in the electrophoresis buffer. The white and black charged particles are driven to move by applying a voltage to the display medium layer, such that each pixel displays a black color, a white color or a gray level. The electrophoretic display device utilizes incident light that irradiates the display medium layer to form reflected light so as to achieve the purpose of display. The incident light may be sunlight or indoor ambient light. Therefore, the electrophoretic display device needs no backlight, which reduces power consumption.
Moreover, a color filter array (CFA) may be adhered to the display medium layer to enable the electrophoretic display device to have a color display function. When light enters or exits from the color filter array, the color resists of the color filter array can filter light with a specific wavelength. For example, after light passes through a red color resist, the color of the light is changed to red. However, when incident light enters the electrophoretic display device having the color display function, the incident light passes through the color resists of the color filter array. Thereafter, the incident light is reflected by the display medium layer to form reflected light, and the reflected light passes through the color resists of the color filter array and out from the display device. As a result, the light passes through the color filter array twice (i.e., via the entrance and exit of the light) such that light loss occurs two times. Hence, the brightness and reflectivity of the electrophoretic display device having the color display function is reduced. In particular, the reflectivity is about 12.
Generally, in order to decrease light loss in the electrophoretic display device having the color display function, a newly designed display medium layer may be used to improve brightness. However, the stability of such a newly designed display medium layer may be poor, and the cost of manufacture is increased. Alternatively, the saturation of the color resists of the color filter array may be reduced to improve the reflectivity of the electrophoretic display device, but this method reduces the color saturation of the electrophoretic display device.